But this isn’t the first time the hermit kingdom has wavered on talks with the U.S. In fact, the move is a lot more consistent with North Korea’s diplomatic strategy, according to Andre Schmid, an associate professor in the University of Toronto’s Department of East Asian Studies.

“Washington got ahead itself,” he said. “This is not going to be easy; North Korea said ‘Don’t just think we are going to just roll over.'”

On Wednesday, North Korea called off high-level talks with South Korea, which was the first sign of trouble after months of warming ties. The nation also threw next month’s summit between Kim and Trump into question, saying it may reconsider if Washington insists it unilaterally gives up its nuclear weapons.

WATCH: White House not surprised by North Korea threat to pull out of summit

The warning marks a deep contrast to the past few months, when both sides embraced efforts to negotiate. North Korea had announced it would publicly shut down its nuclear test site and pledged a new “era of peace.”

Just last week, North Korea also released three U.S. prisoners, with Trump calling Kim an “honourable” person.

So is North Korea suddenly changing its diplomatic tone?

Is this a strategy for North Korea?

“I have to say, this is a little bit out of the blue,” Harry Kazianis, a Korea expert at the Center for the National Interest, told CNN.

“The North Korean pattern is to do provocations whether it is tests of missiles or nukes, ask for negotiations then string us along for months and years,” he said. “But this time, they are not even getting to that point. They are already causing problems before we have the negotiation.”

Joshua Pollack, who is with the Middlebury Institute of International Studies in California, said Pyongyang appeared irritated by the U.S. administration’s vow to maintain sanctions in spite of North Korean concessions.

“The North Koreans want a change in tone from the U.S., and at least so far, they’re not hearing one,” he said.

WATCH: Did North Korea play Donald Trump?

Schmid agrees. North Korea has always talked about denuclearization, but unilateral disarmament has never been part of the deal, he said.

“But for some reason, over the last few months, it’s been interpreted that way,” he said. “There is no doubt that Kim Jong Un wants to put an emphasis on economic growth … but it has its own national interest that we have to try and understand; this is part of a negotiating strategy. And this is not strange to someone like Donald Trump.”

This has happened before

There have been many agreements between the U.S. and North Korea in the past — but they all fell apart because the North refused to follow through on its promises.

1994

In 1994, North Korea and the U.S., under then-president Bill Clinton, signed an “agreed framework” with the goal of freezing and eventually discontinuing Pyongyang’s nuclear program.

In exchange, North Korea is offered the possibility of normalized relations, fuel oil and help building light-water nuclear reactors. But it still violated the agreement.

2003-2009

In January 2003, North Korea’s Kim Jong Il, father of Kim Jong Un, announces Pyongyang will withdraw from the Non-Proliferation Treaty it had agreed to in 1985. Three months later, North Korea announces it has a nuclear weapon.

In hopes of finding a peaceful resolution to the North’s nuclear ambitions, six-party talks begin in Beijing between North Korea, South Korea, China, the U.S., Russia and Japan.

In 2004-05, as the six-nation talks are held intermittently, North Korea continues missile testing. As would become a pattern, Pyongyang offers to curtail its work in exchange for aid while also citing concerns about hostile action from the U.S.

With the talks in abeyance in 2006, the North steps up its missile testing and accuses the U.S. of being a nuclear menace, drawing a warning from then-president George W. Bush.

WATCH: Aerial photographs appear to show North Korea shuttering its nuclear test facility

In 2007, North Korea promised to shut down its nuclear reaction in exchange for fuel oil. But the country’s pledge to disclose all its nuclear activities by the end of the year goes unfulfilled.

2012

In 2012, North Korea agreed to suspend its nuclear weapons program in return of economic help from the U.S. But the country continued to make strides in its nuclear weapons program, causing the agreement to crumble.

Tina Park, executive director of the Canadian Centre for the Responsibility to Protect, said North Korea’s actions are “almost predictable” but it’s also important that all sides (U.S., South Korea and North Korea) make efforts to go ahead with the summit as planned.

“There is more for North Korea to gain to coming to the negotiating table and having a frank conversation about a peace treaty and of a potential withdrawal of U.S. troops out of South Korea,” Park said.

“The root causes of North Korea’s insecurities have to be addressed, and they have to find a common ground,” she added.